The present invention relates to a method for the preparation of a catalyst carrier, to a hydrocarbon desulfurization catalyst prepared using the carrier, and to a process for hydrodesulfurizing a hydrocarbon feedstock using the aforementioned catalyst. More particularly, it relates to a method for the preparation of a porous catalyst substantially free of macropores (diameter above 1000 A.) and containing at least one metal and/or metal compound of Groups VI-B and VIII of the elements. Still more particularly, it relates to a catalyst which comprises a predominantly alumina carrier component which is substantially free of macropores, has a particular micropore size distribution, and contains the aforementioned metal and/or metal compounds, and to a hydrocarbon hydrodesulfurization process using the catalyst.
Porous alumina is often employed as a support material for hydrocarbon hydrodesulfurization catalysts. When the petroleum hydrocarbon feed is more or less free of soluble metal contaminants such as vanadium, nickel, iron, and the like, ordinary porous alumina as known in the art is in general a satisfactory hydrodesulfurization catalyst component. However, with the dwindling world inventory of available and more desirable crude oils, the processor is faced with the necessity of accommodating his process to the use of petroleum feeds which are grossly contaminated with these troublesome impurities. Under the impact of these feeds, previously available hydrodesulfurization catalysts are found to suffer increased fouling rates, reduced catalyst lives and other disadvantages. The metal impurities in particular are found to clog the catalyst pores, thus limiting the catalyst life to the time required to more or less fill the pores with the metal (regeneration by removal of the metal from the pores, being, in general, impractical).
The pressing need for desulfurizing hydrocarbon stocks obtained from petroleum processing is well known. When these stocks are combusted as a fuel in the usual manner, the sulfur present in the hydrocarbon becomes a serious pollutant of the atmosphere in the form of sulfur-oxide gases.
Typical operating conditions for hydrodesulfurization processes include a reaction zone temperature of 600.degree. to 900.degree. F., a pressure of 200 to 3000 psig, a hydrogen feed rate of 500 to 15,000 SCF per barrel of oil feed, and a catalyst such as nickel or cobalt and molybdenum or tungsten on a porous refractory support.